Melem based mesoporous metal-free catalyst for cycloaddition of CO2 to cyclic carbonate

A highly efficient melem based mesoporous metal-free catalyst with amino and hydroxyl groups was successfully developed by template method with melamine as precursor and nano-SiO 2 as template. In the absence of any co-catalyst and solvent, the catalyst mp-CN-450 exhibits high catalytic activity for catalytic cycloaddition reaction between CO 2 and polyfunctional epoxides, and the epoxides conversion and corresponding cyclic carbonates selectivity are 99.7 % and 99.5 %, respectively. And the catalyst has hardly loss of catalytic activity after being reused for four cycles. The characterization results disclose that the high catalytic activity of the catalyst is closely related to its large specific surface area, abundant mesoporous structure and synergistic effect of N species and hydroxyl groups of melem hydrates. Additionally, through the study of different N-containing compounds, it was found that the primary amine may underwent a ring-opening reaction with epoxide. But with the addition of CO 2 , amine groups prior to reacted with CO 2 to form carbamate salt, avoided the formation of by-products, thereby improved the selectivity of cyclic carbonate. Finally, based on the above research, a possible reaction mechanism for the coupling of CO 2 to epoxides was proposed. • A melem based mesoporous heterogeneous catalyst was prepared by template method. • The catalyst exhibited high catalytic activity and stability for CO 2 cycloaddition. • The reaction was catalyzed by metal-free catalyst without any cocatalyst and solvent. • Melem hydrate provided different amino and hydroxyl active sites in the reaction. • Effect of different N-containing species on cycloaddition reaction was investigated.